This recipe is courtest of The Daily Meal Staff
Heat your grill to medium heat.
Clean the mushrooms with a damp paper towel. Dry well.
Remove the black gills using a spoon. Using your hands rub oil on the outside of the mushroom.
In a large mixing bowl, combine softened cream cheese, cheddar, garlic powder, and spinach. Add salt and pepper to taste.
Divide cheese mixature between the three prepared mushroom caps. Place on the frill, cover and cook for about 10 minutes.